Showing papers on "Catalase published in 1980"

Oxygen metabolism and the toxic properties of phagocytes.

Abstract: The products of oxygen reduction (superoxide anion, hydrogen peroxide, hydroxyl radicals) and excitation (singlet oxygen) have been implicated in the toxic properties of phagocytes (neutrophils, eosinophils, and mononuclear phagocytes). Enzymes that potentiate (such as peroxidase) or limit (such as catalase, superoxide dismutase) the toxicity of these agents contribute to the complexity of the oxygen-dependent antimicrobial systems of phagocytes. These toxic systems are dormant when the phagocyte is at rest but are activated when the need arises and directed to the destruction of invading microorganisms and other foreign cells. Occasionally, the toxic systems are directed against normal host cells and in this way contribute to the pathogenesis of disease.

Enzymatic Defenses of the Mouse Heart Against Reactive Oxygen Metabolites: ALTERATIONS PRODUCED BY DOXORUBICIN

Abstract: The endogenous defenses of the mouse heart against reactive oxygen metabolites were investigated. The activities of three enzymes capable of detoxifying activated oxygen were determined in both the heart and liver; cardiac muscle contains 150 times less catalase and nearly four times less superoxide dismutase than liver. Glutathione peroxidase activities were, however, similar to the two tissues. Assay of glutathione peroxidase in the heart after 6 wk of selenium depletion with both hydrogen peroxide and cumene hydroperoxide as substrates revealed a >80% drop in enzyme activity and gave no indication that murine cardiac tissue contains nonselenium-dependent glutathione peroxidase. The selenium-deficient state, which was characterized by markedly decreased cardiac glutathione peroxidase levels, led to significantly enhanced doxorubicin toxicity at a dose of 15 mg/kg i.p. Doxorubicin administration in selenium-sufficient animals resulted in a dose-dependent decrease in cardiac glutathione peroxidase activity; the decrease in enzyme activity lasted 72 h after 15 mg/kg i.p. In contrast, cardiac superoxide dismutase and hepatic superoxide dismutase and glutathione peroxidase were unaffected by this dose of doxorubicin. These results suggest that the major pathway in cardiac tissue for detoxification of reactive oxygen metabolites is via the concerted action of superoxide dismutase and selenium-dependent glutathione peroxidase. The latter enzyme may be depleted by a selenium-deficient diet or doxorubicin treatment, leaving the heart with limited mechanisms for disposing of hydrogen peroxide or lipid peroxides.

Macrophage-mediated suppression. I. Evidence for participation of both hdyrogen peroxide and prostaglandins in suppression of murine lymphocyte proliferation.

Abstract: Macrophage-mediated suppression of Con A induced proliferation of murine splenic lymphocytes was studied in vitro. Either Corynebacterium parvrum-induced peritoneal exudate cells (PEC) or thioglycollate-induced PEC could totally suppress lymphocyte proliferation at a PEC:lymphocyte ratio of 2:10, whereas a ratio of 1 to 1.5: 10 caused a partial (60 to 68%) suppression. Exogenous PGE1 and PGE2 at concentrations of 10(-8) to 10(-6) M could not totally suppress lymphocyte proliferation. Conversely, indomethacin reversed the partial suppression by macrophages but only partially protected the totally suppressed lymphocyte cultures. Macrophage-mediated cytotoxicity and cytostasis have been proposed to be mediated by hydrogen peroxide. Therefore, hydrogen peroxide was investigated as a possible additional cause for macrophage-mediated suppression, by testing the anti-inhibitory effects of catalase. Partially suppressed cultures were effectively protected from suppression by catalase. In totally suppressed cultures, catalase alone was only minimally effective, but a synergistic effect of catalase and indomethacin was obtained, which provided complete protection from maximal macrophage-mediated suppression. Catalase presumably contributes to the reversal of macrophage suppressive effects both by reducing the direct toxic effect of H2O2 and by preventing the H2O2 from generating additional prostaglandins.

Responses of superoxide dismutase and glutathione reductase activities in cotton leaf tissue exposed to an atmosphere enriched in oxygen.

Abstract: Responses of superoxide dismutase (EC 1.15.1.1) and glutathione reductase (EC 1.6.4.2) activities were evaluated in leaf tissue from intact cotton plants (Cotton Branch 1697) which were exposed to 75% O(2), 350 microliters per liter CO(2) for 48 hours. Soluble protein was extracted from O(2)-treated and control tissue, and enzyme levels were determined. Superoxide dismutase activity in cotton leaf tissue was high (26 units per milligram protein) under normal conditions of 21% O(2), saturating light, and limiting CO(2), and neither qualitative nor quantitative differences in the cyanide-sensitive or -insensitive forms of the enzyme occurred in response to hyperoxic conditions. Glutathione reductase activity, however, was 2- to 3-fold higher in extracts from tissue exposed to 75% O(2). No increase in activity was observed for the peroxisomal enzymes, glycolate oxidase (EC 1.1.3.1) and catalase (EC 1.11.1.6). Results are consistent with an integrated pathway involving superoxide dismutase and glutathione reductase for protection of sensitive leaf components against detrimental effects of intermediate reduction products of O(2).

Macrophage microbicidal activity. Correlation between phagocytosis-associated oxidative metabolism and the killing of Candida by macrophages.

Abstract: The mechanisms by which macrophages kill ingested microorganisms were explored using Candida albicans and Candida parapsilosis. The results indicate that efficient macrophage candidacidal activity depends upon the generation of oxygen metabolites by the phagocytic cell: (a) peritoneal macrophages from mice infected with bacillus Calmette-Guerin (BCG) or injected intraperitoneally with lipopolysaccharide (LPS) released more superoxide anion (0(2)(-)) during phagocytosis of candida and killed candida better than did resident macrophages; (b) cells of the macrophage-like line J774.1, which released negligible amounts of O(2)(-), could ingest the candida normally but not kill them; (c) killing of candida by resident, LPS- elicited, and BCG-activated macrophages was inhibited by agents that scavenge O(2)(-), hydrogen peroxide (H(2)0(2)), hydroxyl radical (x OH), and singlet oxygen; and (d) all three macrophage types killed C. parapsilosis more effectively than C. albicans, and (7. parapsilosis stimulated a more prompt and vigorous burst of macrophage oxygen consumption and 0(2)(-) release than did C. albicans. Macrophages ingested C. parapsilosis slightly more quickly than C. albicans, but phagocytosis of both strains was equivalent by 60 min of incubation. Although C. albicans contained higher concentrations of the oxygen-metabolite scavengers superoxide dismutase and catalase, neither fungal species scavenged 0(2)(-) or H(2)0(2) effectively; and C. albicans was killed more easily than C. parapsilosis by a xanthine oxidase system that generates primarily H(2)O(2) at pH 7, or 0(2)(-) and x OH at pH 10. Thus, the decreased killing of C. albicans appears to result primarily from the capability of this species to elicit less vigorous stimulation of macrophage oxidative metabolism. This capability may have general relevance to the pathogenicity of microorganisms.

Peroxide Levels and the Activities of Catalase, Peroxidase, and Indoleacetic Acid Oxidase during and after Chilling Cucumber Seedlings

Abstract: The activities of catalase, peroxidase, indoleacetic acid (IAA) oxidase and peroxide levels in cucumber plants during and after chilling were determined. During 96 hours at 5 C and 85% relative humidity, catalase activity declined, IAA oxidase activity increased, and peroxide concentrations increased. Peroxidase activity was not affected by chilling. When chilled plants were returned to 25 C to recover, enzyme activities and peroxide concentration were restored to their prechilling levels. The increase in peroxide and IAA oxidase activity may inactivate or destroy IAA and thus retard growth.

Hydrogen peroxide production by rat brain in vivo.

Abstract: H2 O2 production by rat brain in vivo was observed with a method based on the measurement of brain catalase. The administration to the rat of 3-amino-1, 2, 4-triazole, an H2 O2- dependent inhibitor of catalase, caused progressive inhibition of brain catalase activity in both the supernatant and pellet fractions of homogenates of the striatum and prefrontal cortex. The prevention of catalase inhibition by prior administration of ethanol confirmed that catalase inhibition in vivo was dependent upon H2 O2. A significant portion of the catalase (30-33%) appeared in the supernatant fraction from a slow-speed homogenization procedure and was not significantly contaminated by either erythrocytes or capillaries. In the whole homogenate, less than 6% of the catalase activity was attributed to erythrocytes. Modification of intracellular monoamine oxidase activity by either pargyline or reserpine did not change the rate of inhibition of catalase by aminotriazole. A probable interpretation of these data is that H2 O2 generated by mitochondrial monoamine oxidase does not reach the catalase compartment; the catalase is contained in particles described by other investigators as the microperoxisomes of brain. In studies in vitro, the production of H2 O2 by rat brain mitochondria with either dopamine or serotonin as substrate was confirmed.

Role of oxygen-dependent mechanisms in antibody-induced lysis of tumor cells by activated macrophages*

Abstract: The alloantiserum-dependent lysis of TLX9 lymphoma cells by peritoneal cells from Bacille Calmette-Guerin (BCG)-treated mice was inhibited 62 percent by depletion of oxygen. This effect did not appear to be a result of interference with mitochondrial respiration because cyanide, azide, and dinitrophenol did not inhibit cytotoxicity. Preincubating the effector cells for 2 h without glucose, which markedly reduces their ability to release hydrogen peroxide, likewise suppressed antibody-dependent cytolysis by 62 percent. Lysis of sensitized lymphoma cells was virtually abolished by 6 mg/ml of thioglycollate broth, a concentration that also abrogated the detectable release of hydrogen peroxide and the lysis of lymphoma cells by BCG-activated macrophages in response to phorbol myristate acetate (PMA). This concentration of thioglycollate broth was not toxic to the effector cells, as judged by adherence to plastic, binding of opsonized erythrocytes, and phagocytosis of radiolabeled starch granules. Catalase, superoxide dismutase, horseradish peroxidase, mannitol, ethanol, benzoate, and diazabicyclooctane were without consistent effects. Cytochalasin B and dihydrocytochalasin B both markedly suppressed cytolysis, whether induced by antibody or by PMA (ID(50), 0.5 μg/ml). Cytoehalasin B was an equally potent suppressor of glucose uptake and PMA-induced hydrogen peroxide release by BCG-activated macrophages (ID(50), 0.5 μg/ml). However, dihydrocytochalasin B lacked these latter effects, which suggests that cytotoxicity required intact contractile elements. The extracellular lysis of antibody-coated lymphoma cells by BCG-activated macrophages appears to have a predominantly oxidative basis.

Deficient Metabolic Utilization ofHydrogen Peroxide inTrypanosoma cruzi

Abstract: Theglutathione peroxidase-glutathione reductase system, an alternative pathway for metabolic utilization ofH202[Chance, Sies& Boveris (1979) Physiol. Rev.59, 527-6051, was investigated inTrypanosoma cruzi, an organism lacking catalase and deficient inperoxidase [Boveris & Stoppani (1977) Experientia 33,1306-13081. The presenceofglutathione (4.9 +0.7nmolofreduced glutathione/108 cells) andNADPHdependent glutathione reductase (5.3 + 0.4munit/108 cells) was demonstrated inthe cytosolic fraction oftheparasite, butwithH202as substrate glutathione peroxidase activity could notbedemonstrated inthesame extracts. Witht-butyl hydroperoxide or cumene hydroperoxide as substrate, a very lowNADPH-dependent glutathione peroxidase activity was detected (equivalent to0.3-0.5 munitofperoxidase/108 cells, or about10%ofglutathione reductase activity). Blankreactions oftheglutathione peroxidase assay(non-enzymic oxidation ofglutathione byhydroperoxides andenzymic oxidation ofNADPH)hampered accurate measurementofperoxidase activity. The presenceofsuperoxide dismutase andascorbate peroxidase activity in, aswell asthe absence ofcatalase from, epimastigote extracts was confirmed. Ascorbate peroxidase activity was cyanide-sensitive andheat-labile, butno activity couldbedemonstrated

Inhibition of alloxan action in isolated pancreatic islets by superoxide dismutase, catalase, and a metal chelator.

Abstract: The possible participation of superoxide anions, hydrogen peroxide, and hydroxyl radicals in the action of alloxan was investigated using isolated rat pancreatic islets. Exposure of islets for 5 min to alloxan (0.15 or 0.2 mg/ml) inhibited subsequent glucose-stimulated insulin release. The presence of superoxide dismutase (1000 U/ml), catalase (50 μg/ml), or a metal chelator diethylenetriaminepentacetic acid (1 mM) markedly attenuated this effect of alloxan. Use of these agents afforded complete protection from the lower concentration of alloxan and partial protection from the higher concentration of the toxic compound. Inactivation of the enzymes or addition of excess iron to the chelating agent before its use with alloxan eliminated the protective action of these agents. The results are consistent with the proposal that hydroxyl radicals, generated via reactions that involve superoxide anions, hydrogen peroxide, and iron, mediate the deleterious effect of alloxan in pancreaticislets.

Damage to Candida albicans Hyphae and Pseudohyphae by the Myeloperoxidase System and Oxidative Products of Neutrophil Metabolism In Vitro

Abstract: In previous studies, we noted that Candida hyphae and pseudohyphae could be damaged and probably killed by neutrophils, primarily by oxygen-dependent nonphagocytic mechanisms. In extending these studies, amount of damage to hyphae again was measured by inhibition of [(14)C]cytosine uptake. Neutrophils from only one of four patients with chronic granulomatous disease damaged hyphae at all, and neutrophils from this single patient damaged hyphae far less efficiently than simultaneously tested neutrophils from normal control subjects. Neutrophils from neither of two subjects with hereditary myeloperoxidase deficiency damaged the hyphae. This confirmed the importance of oxidative mechanisms in general and myeloperoxidase-mediated systems in particular in damaging Candida hyphae. Several potentially fungicidal oxidative intermediates are produced by metabolic pathways of normal neutrophils, but their relative toxicity for Candida hyphae was previously unknown. To help determine this, cell-free in vitro systems were used to generate these potentially microbicidal products. Myeloperoxidase with hydrogen peroxide, iodide, and chloride resulted in 91.2% damage to hyphal inocula in 11 experiments. There was less damage when either chloride or iodide was omitted, and no damage when myeloperoxidase was omitted or inactivated by heating. Azide, cyanide, and catalase (but not heated catalase) inhibited the damage. Systems for generation of hydrogen peroxide could replace reagent hydrogen peroxide in the myeloperoxidase system. These included glucose oxidase, in the presence of glucose, and xanthine oxidase, in the presence of either hypoxanthine or acetaldehyde. In the presence of myeloperoxidase and a halide, the toxicity of the xanthine oxidase system was not inhibited by superoxide dismutase and, under some conditions, was marginally increased by this enzyme. This suggested that superoxide radical did not damage hyphae directly but served primarily as an intermediate in the production of hydrogen peroxide. The possible damage to hyphae by singlet oxygen was examined using photoactivation of rose bengal. This dye damaged hyphae in the presence of light and oxygen. The effect was almost completely inhibited by putative quenchers of singlet oxygen: histidine, tryptophan, and 1,4-diazobicyclo[2.2.2]octane. These agents also inhibited damage to hyphae by myeloperoxidase, halide, and either hydrogen peroxide or a peroxide source (xanthine oxidase plus acetaldehyde). Myeloperoxidase-mediated damage to hyphae was also inhibited by dimethyl sulfoxide, an antioxidant and scavenger of the hydroxyl radical. These data support the involvement of oxidative mechanisms and the myeloperoxidase-H(2)O(2)-halide system, in particular in damaging hyphae in vitro and perhaps in vivo as well.

Metabolism of hydrogen peroxide in Euglena gracilis Z by L-ascorbic acid peroxidase.

Abstract: Euglena gracilis was found to contain a peroxidase that specifically require L-ascorbic acid as the natural electron donor in the cytosol. The presence of an oxidation-reduction system metabolizing L-ascorbic acid was demonstrated in Euglena cells. Oxidation of L-ascorbic acid by the peroxidase, and the absence of ascorbic acid oxidase activity, suggests that the system functions to remove H2O2 in E. gracilis, which lacks catalase.

Ethanol Oxidation by Rat Brain in Vivo

Abstract: Can brain metabolize ethanol? We present data demonstrating that brain catalase in conjunction with endogenous H2O2 will oxidize ethanol in vivo. The method is based on an H2O2-dependent inhibition of brain catalase in vivo by 3-amino-1,2,4-triazole and its prevention by ethanol. The irreversible inhibition of catalase by aminotriazole is known to proceed via the reaction of (catalase-H2O2) compound I with aminotriazole. Inhibition can be prevented by compounds that are oxidized by compound I. Ethanol is one such compound. Prevention of the inhibition of brain catalase in vivo by prior administration of ethanol constitutes indirect evidence for the oxidation of ethanol to acetaldehyde in rat brain. The catalase content of the tissues represented catalase in the brain parenchyma, from which erythrocytes and capillaries had been excluded. Ethanol did not alter the levels of aminotriazole in brain. These results constitute the first demonstration of ethanol oxidation by living brain.

Generation of a chemotactic lipid from arachidonic acid by exposure to a superoxide-generating system

Abstract: Certain products of arachidonic acid have been demonstrated recently to possess chemotactic activity for human polymorphonuclear leukocytes (PMN). Enzymatic (lipoxygenase, cyclooxygenase) generation of these lipid chemotaxins proceeds through the formation of intermediate lipid peroxides. Since lipid peroxidation can be mediated by oxygen-derived free radicals, we have examined whether chemotactically active products of arachidonic acid could be produced by exposing this unsaturated fatty acid to a superoxidegenerating system. A lipid with potent chemotactic activity for human PMN was produced by incubating arachidonic acid with xanthine oxidase and acetaldehyde. Generation of chemotactic activity was time-dependent and could be inhibited to the greatest extent by scavengers of singlet oxygen (i.e., histidine, uric acid, and 2,5-dimethylfuran). Inhibition was also observed with scavengers of superoxide anion radicals (i.e., superoxide dismutase), hydrogen peroxide (i.e., catalase), and hydroxyl radicals (i.e., mannitol). Silica gel thin-layer radiochromatography demonstrated a single peak with chemotactic activity (Rf = 0.33–0.38) distinct from unaltered arachidonic acid. The product of arachidonic acid was chemotactic at a concentration of 3.0 ng/ml and chemokinetic at concentrations of 0.75–1.5 ng/ml. Since PMN produce oxygen-derived free radicals and singlet oxygen upon stimulation of their plasma membrane, and since arachidonic acid is widely distributed in human tissues, free radical-mediated generations of chemotactic activity from arachidonic acid may play an important role in amplifying inflammatory responses.

The recA+ gene product is more important than catalase and superoxide dismutase in protecting Escherichia coli against hydrogen peroxide toxicity.

Abstract: Various deoxyribonucleic acid repair-deficient strains of Escherichia coli K-12 were exposed to hydrogen peroxide under anaerobic conling of the strains was determined. The level of catalase, peroxidase, and superoxide dismutase in cell-free extracts of the strains as well as the capacity of intact cells to decompose hydrogen peroxide were assayed, recA strains were more rapidly killed than other strains with deoxyribonucleic acid repair deficiencies. There was no correlation between the killing rate of the strains and the capacity of intact cells to decompose hydrogen peroxide or the level of catalase and superoxide dismutase in cell-free extracts. The level of peroxidase in cell-free extract was too low to be determined.

Protection of Human Neutrophils by Endogenous Catalase: STUDIES WITH CELLS FROM CATALASE-DEFICIENT INDIVIDUALS

Abstract: To investigate the importance of catalase as a protecting enzyme against oxidative damage in phagocytic leukocytes, we have tested the functional capacity of neutrophils from two individuals homozygous for Swiss-type acatalasemia and from two individuals heterozygous for this deficiency. In the former cells, 25-30% of residual activity of catalase was present. In the latter cells, the values were close to normal. Chemotaxis towards casein, release of lysosomal enzymes and hydrogen peroxide during phagocytosis of zymosan, and intracellular killing of Staphylococcus aureus were normal in all cells tested. Inhibition of heme enzymes with azide (2 mM) enhanced the respiration and hexose monophosphate shunt activity of normal, but not of homozygous acatalasemic, neutrophils. This indicates that the enhancement in normal cells is, at least in part, due to catalase inhibition. After 15 min preincubation with an H2O2-generating system (glucose plus glucose oxidase), the respiratory response to zymosan phagocytosis was strongly depressed in the homozygous acatalasemic and in normal, azide-treated neutrophils, but not in normal, untreated cells. Under these conditions, the release of lysosomal enzymes was depressed and that of lactate dehydrogenase enhanced, in catalase-deficient and in catalase-inhibited, but not in normal, neutrophils. During prolonged incubation with the H2O2-generating system (30-60 min), the reduction level of intracellular glutathione remained high and the hexose monophosphate shunt continued to operate normally in all cells tested. Thus, although the function of neutrophils without catalase activity was depressed by extracellular hydrogen peroxide, the H2O2 degradation via the glutathione redox system remained operative. The results indicate that the glutathione redox system by itself efficiently protects phagocytosing neutrophils against their own oxidative products. During heavy external oxidative stress, however, both catalase and the glutathione redox system are needed for adequate protection.

Cold adaptation in the rat: increased brown fat peroxisomal beta-oxidation relative to maximal mitochondrial oxidative capacity

Abstract: Brown fat hypertrophy in the rat resulting from cold adaptation is shown here to involve increased mitochondrial, peroxisomal, and lysosomal enzyme activities. Mitochondrial activity in homogenates of brown fat was estimated as cytochrome c oxidase. After 4 wk in the cold (+5 C), the total activity was 3-fold higher than in control rats, although the specific activity was somewhat lower. Peroxisomal activity was followed as cyanide-insensitive palmitoyl-CoA-dependent NAD+ reduction (palmitoyl-CoA oxidase) and as catalase. The total activity of both palmitoyl-CoA oxidase and catalase was more than 10-fold higher than in controls and the specific activity about 3-fold higher. Acid phosphatase, used as a lysosomal marker, showed a 6-fold higher total activity and almost twice as high specific activity. The relatively greater increase in peroxisomes and lysosomes compared with mitochondria indicates an involvement in thermogenesis also for these organelles.

Oxygen utilization by Lactobacillus plantarum

Abstract: Lactobacillus plantarum (ATCC 8014) cells, grown aerobically on glucose medium, consumed molecular oxygen when incubated with either glucose, d/l-lactate or pyruvate as substrate. Cell extracts catalyzed the oxidation of NADH, d/l-lactate or pyruvate with O2. Per mol O2 2mol of NADH were consumed indicating that O2 was reduced to H2O; reduction proceeded via H2O2 involving a NADH oxidase and a NADH peroxidase. Catalase activity was absent. Pyruvate oxidation with O2 led to the formation of H2O2, lactate oxidation to the formation of H2O. Thus in L. plantarum different mechanisms are available by which molecular oxygen can be used as electron acceptor for oxidation reactions.

Macrophage oxygen-dependent antimicrobial activity. IV. Role of endogenous scavengers of oxygen intermediates.

Abstract: The activities of the endogenous O2- and H2O2 scavenging enzymes, superoxide dismutase (SOD), glutathionine peroxidase (GP), and catalase, were measured in lysates of the intracellular parasite, Toxoplasma gondii, and in various macrophage populations. During 72 h of cultivation in standard medium alone, the catalase activity of in vivo-activated toxoplasma-immune macrophages (IM) and immune-boosted macrophages (IB) progressively increased by eight- to ninefold, and correlated with the previously observed parallel decline in these cells' antitoxoplasma activity and capacity to release H2O2. SOD and GP activities either remained constant or decreased during this 3-d period. Lymphokine exposure, which preserved the antitoxoplasma activity and oxidative capacity of 48- and 72-h cultures of IB and IM cells, blunted the rise in catalase levels and had no effect on SOD or GP. Inhibition of IB and IM macrophage catalase by aminotriazole maintained toxoplasmastatic activity otherwise lost after 48 h of cultivation. In addition, IB and IM cells from acatalasemic mice contained 20- to 30-fold less catalase, and showed comparatively little decline in either H2O2 release or antitoxoplasma activity during 72 h in culture. In vitro-(lymphokine) activated resident macrophages from normal mice had the highest levels of SOD, GP, and catalase, and these cells failed to kill or inhibit T. gondii despite enhanced extracellular release of O2- and H2O2. Toxoplasmas were also found to contain all three enzymatic scavengers. Aminotriazole inhibition of lymphokine-activated cells' catalase or of toxoplasma catalase was effective in inducing these macrophages to display antitoxoplasma activity. Moreover, and in contrast to normocatalasemic resident cells, those from acatalesemic mice were readily induced by lymphokine to inhibit the replication of untreated virulent toxoplasmas. These results suggest that endogenous O2- and H2O2 scavenging enzymes, which function within both T. gondii and activated macrophages as host cell antioxidant protective mechanisms, may reduce the effectiveness of phagocyte antimicrobial activity. Thus, the presence of SOD, GP, and especially catalase within both target and effector cell may be important determinants of macrophage oxygen-dependent processes.

Antiinflammatory effects of free radical scavengers and antioxidants: further support for proinflammatory roles of endogenous hydrogen peroxide and lipid peroxides.

Abstract: Scavengers of reactive oxygen species were tested by local administration during granulomatous inflammation in the rat, induced by the subdermal implantation of carrageenin-soaked sponges. Drugs were administered either in a single dose immediately after sponge implantation, or in daily doses on days 3–6 of inflammation. The effects of the injected drugs were assessed using the day 7 granuloma. When given at the moment of sponge implantation, catalase showed antiinflammatory effects, whereas Superoxide dismutase did not. However, the addition of Superoxide dismutase to catalase, prior to injection, markedly potentiated the inhibition of granuloma formation by catalase alone. Negative results obtained with scavengers of hydroxyl radicals and singlet molecular oxygen suggest that protection of superoxide dismutase by catalase from inactivation by hydrogen peroxide, is a likely explanation for the observed potentiation. When administered at the moment of the induction of inflammation,α-tocopherol and propyl gallate, both antioxidants, also inhibited granuloma formation. All drugs tested were either ineffective or even enhanced granuloma weight following administration into a preformed granuloma. An inhibitor of both pathways of arachidonate metabolism, phenidone, inhibited granuloma formation irrespective of the moment of administration. The results presented in this paper suggest proinflammatory roles for hydrogen peroxide and lipid peroxides and a possible involvement of hydroxyl radicals and singlet oxygen in the breakdown of collagen.

Direct oxidases and related enzymes

Abstract: Publisher Summary The chapter discusses the enzymic activity of ascorbate oxidase (AO) and polyphenol oxidase (PPO) and describes their physiological function. AO catalyzes the oxidation of ascorbate by molecular oxygen. The oxidase has an absolute requirement for molecular oxygen and produces water only. H 2 O 2 is not a product of the oxidation but appears to be formed as the result of a secondary, slow catalytic reaction, leading to an irreversible inactivation of the purified enzyme, unless protective agents such as gelatin or native catalase are added. The inactivation is not observed with crude plant extracts. Enzymic oxidation does not proceed beyond dehydroascorbate, which is, however, unstable in alkaline solution. A wide range of copper-complexing agents inhibit the enzyme. PPO from many plant sources is inhibited by the whole range of copper-chelating agents, among which cyanide and diethyldithiocarbamate have been most extensively used. Cyanide has been shown to compete with molecular oxygen, demonstrating the presence of copper in the oxygen-binding site. PPO is often described as a soluble enzyme, from which it might be inferred that it is localized predominantly, if not exclusively, in the cytosol of plant cells.

Oxidative mechanisms of monocyte-mediated cytotoxicity.

Abstract: Human monocytes stimulated with phorbol myristate acetate were able to rapidly destroy autologous erythrocyte targets. Monocyte-mediated cytotoxicity was related to phorbol myristate acetate concentration and monocyte number. Purified preparations of lymphocytes were incapable of mediating erythrocyte lysis in this system. The ability of phorbol myristate acetate-stimulated monocytes to lyse erythrocyte targets was markedly impaired by catalase or superoxide dismutase but not by heat-inactivated enzymes or albumin. Despite a simultaneous requirement for superoxide anion and hydrogen peroxide in the cytotoxic event, a variety of hydroxyl radical and singlet oxygen scavengers did not effect cytolysis. However, tryptophan significantly inhibited cytotoxicity. The myeloperoxidase inhibitor cyanide enhanced erythrocyte destruction, whereas azide reduced it modestly. The inability of cyanide to reduce cytotoxicity coupled with the protective effect of superoxide dismutase suggests that cytotoxicity is independent of the classic myeloperoxidase system. We conclude that monocytes, stimulated with phorbol myristate acetate, generate superoxide anion and hydrogen peroxide, which together play an integral role in this cytotoxic mechanism.

Oxidation of Methionine by Human Polymorphonuclear Leukocytes

Abstract: Studies of the photosensitized oxidation have demonstrated that photodynamic oxidation of methionine is mediated by singlet oxygen (1O2). In this study, we demonstrated that phagocytosing human polymorphonuclear leukocytes (PMN), but not resting PMN, oxidized both intracellular and extracellular methionine to methionine sulfoxide. N-ethylmaleimide, which inhibits phagocytosis and cellular metabolism, inhibited the oxidation of methionine. Neutrophils from patients with chronic granulomatous disease did not oxidize methionine even in the presence of phagocytosis. The oxidation of methionine by phagocytosing normal PMN was inhibited by 1O2 quenchers, (1.4-diazabicyclo-[2,2,2]-octane, tryptophan, NaN3), myeloperoxidase (MPO) inhibitors (NaN3, KCN) and catalase. In contrast, superoxide dismutase, ethanol, and mannitol had no effect. Furthermore, 1O2 quenchers did not interfere with the production of superoxide (O2−) by phagocytosing PMN. The combination of catalase and SOD did not enhance the inhibition of methionine by phagocytosing PMN. On the other hand, deuterium oxide stimulated the oxidation of methionine by PMN almost 200%. H2O2 at high concentrations oxidized methionine to methionine sulfoxide. However, when similar amounts of H2O2 were added to human PMN, they did not oxidize methionine. In contrast, when H2O2, at concentrations too low to oxidize methionine by itself, was added to the granular fraction, but not the soluble fraction, they oxidized methionine to methionine sulfoxide. The oxidation of methionine by the combination of H2O2 and granular fractions was inhibited by 1O2 quenchers and MPO inhibitors, but it was stimulated by deuterium oxide. Removal of chloride anion also prevented the oxidation of methionine by the granular fractions. Our results suggest that the oxidation of methionine by phagocytosing PMN is dependent on the MPO-mediated antimicrobial system (MPO-H2O2-Cl−). They also suggest, but do not prove that the oxidation of methionine is mediated by 1O2. Oxidation of methionine may be one of the mechanisms that human PMN damage microorganisms.